It is conventional to provide electrical boxes with knockouts or with cable clamps, or both, to permit the entry of cable into the box under various circumstances. Generally speaking, such cable clamps extend across a port through which cable can be passed, each clamp being hinged at one end so that it can be swung inwardly into the interior volume of the box to open the port and thereby permit entry of the cable. The clamp can be provided with serrations or teeth to engage the outer insulation on the cable and prevent its inadvertent extraction.
While such a box is built to permit this hinging action, there is intentionally some resistance to swinging the clamp inwardly, at least the first time, so that an unused clamp will maintain a reasonably secure closure for its associated port. When the box is particularly deep as compared with the cross sectional area of its open side, getting a grip on the clamp, particularly if the box has already been installed in a wall, ceiling or the like, can be somewhat difficult and may require a special tool of some kind.